Advice needed - overheating problem

[brianmacza]

Ok... After I started the rebuild on my XX (post dropping it in July) I decided to get the local radiator guys to MAKE me a copper replacement rather than get shafted by the stealership (the handmade version in copper is 1/4 the price of the OEM unit from HONDA) cos there was LOTS to pay for.

THe radiator is slightly deeper, has the same number of tubes from intake tank to outlet tank - painted matt black, it weighs fractionally more but thats of no concern.

QUESTION: Does aliminium have better thermal transfer properties than copper? Is the black paint causing trouble for me?

The thermostat decided to die (the fan switch in the outlet tank) so I put in a bridge switch to earth to force the fan on. If its a hot day, a 35km ride on freeway with nominal traffic at my usual pace (140 to 180kph) with the fan forced ON end up with the bike upchucking about 1/2 cup of coolant when the engine is stopped (not immediately tho... about 2 minutes after the motor has been stopped).

Wisdom is needed...

[97xxca]

When i had my XX serviced one time, the dealer mechanic reversed the overflow hose and the vent hose. They are both the same size right under the radiator cap. It would burp out coolant whenever i shut off the motor. You might double check those hoses.

[TuffguyF4i]

1st,, how do you know it is overheating? Are you going by the gauging on the bike, or by the bike kicking out fluid?

Normally, bikes boil over because the cap on the radiator isn't keeping in the pressure and that decreases the boiling point of fluid.

Start with the cap. Make sure its not damaged and meets the stock radiator needs.

[blackhawkxx]

QUESTION: Does aliminium have better thermal transfer properties than copper?

I have always read that copper does a better job at transferring the heat. Here is a little bit that I found.

Aluminum vs. Copper-Brass

Many new performance radiators, such as those from Griffin and Be Cool, are made from aluminum that offers weight savings over copper-brass. While aluminum does not dissipate heat as well as copper-brass, modern radiator design more than makes up for the difference. Old copper-brass radiators were soldered together, but solder is a poor thermal conductor and this reduced the ability of the fins to remove heat from the tubes.

[Zero Knievel]

Does your cooling fan kick in reliably?

I've noticed (1) that the fan switches on sport bikes kick in way too late to effectively keep the motor cool as some wait until you're almost at boil over to kick in and (2) many fan switches just don't work reliably in the first place. Of the two sport bikes I've owned (Kawasaki and Honda), I've always had to wire in a manual bypass so I can kick the fan on rather than wait for the switch to do its job.

[Redbird]

Does your cooling fan kick in reliably?

I've noticed (1) that the fan switches on sport bikes kick in way too late to effectively keep the motor cool as some wait until you're almost at boil over to kick in and (2) many fan switches just don't work reliably in the first place. Of the two sport bikes I've owned (Kawasaki and Honda), I've always had to wire in a manual bypass so I can kick the fan on rather than wait for the switch to do its job.

Serious question- do you bother reading threads before posting in them?

[Iceman_40]

Based only on metal yes copper is better than Alum. Design means more than the metal.

Paint will insulate the copper that is for sure, I don't know how much though.

With the fan turned off can you ride on the highway(65MPH) and keep the engine temps at a normal temp?

On the highway my fan NEVER turns on, there is no need for it to be on as much more air is moving throw the rad then the fan could supply. My bike has never seen over 85C on the highway, fan doesn't normally turn on until 100C.

[brianmacza]

Based only on metal yes copper is better than Alum. Design means more than the metal.

Paint will insulate the copper that is for sure, I don't know how much though.

With the fan turned off can you ride on the highway(65MPH) and keep the engine temps at a normal temp?

On the highway my fan NEVER turns on, there is no need for it to be on as much more air is moving throw the rad then the fan could supply. My bike has never seen over 85C on the highway, fan doesn't normally turn on until 100C.

My temp guage isn't too accurate - it NEVER gets to the upper ranges (1997 model) and my impression is that the heat rises quite dramatically between the offramp on the motorway and my home (about 3 miles with 2 traffic light intersections that almost always catch me)

Will have to yank the radiator and clean off the paint - thinners might do the job assisted with a pressure wash

[rockmeupto125]

.....end up with the bike upchucking about 1/2 cup of coolant when the engine is stopped (not immediately tho... about 2 minutes after the motor has been stopped).

Ummm...where is the upchucking from, and where does the upchucking go?

[Zero Knievel]

Does your cooling fan kick in reliably?

I've noticed (1) that the fan switches on sport bikes kick in way too late to effectively keep the motor cool as some wait until you're almost at boil over to kick in and (2) many fan switches just don't work reliably in the first place. Of the two sport bikes I've owned (Kawasaki and Honda), I've always had to wire in a manual bypass so I can kick the fan on rather than wait for the switch to do its job.

Serious question- do you bother reading threads before posting in them?

Don't remember....I have a short attention span and I usually post when I'm tired.

[brianmacza]

.....end up with the bike upchucking about 1/2 cup of coolant when the engine is stopped (not immediately tho... about 2 minutes after the motor has been stopped).

Ummm...where is the upchucking from, and where does the upchucking go?

The upchuck comes from the header bottle - its not steaming hot water, but I'm assuming its propelled by a bubble of steam from the radiator past the 0.9 bar radiator cap pressure spring...

erm... it lands on the floor

[rockmeupto125]

Is there enough coolant in the bottle so that as the system cools, it can draw back fluid rather than air?

You wouldn't think that you'd have a flow problem with a new core.

[redxxrdr]

The upchuck comes from the header bottle - its not steaming hot water, but I'm assuming its propelled by a bubble of steam from the radiator past the 0.9 bar radiator cap pressure spring...

erm... it lands on the floor

Was your overflow bottle full when you started? or filled to the cold fill level?

My bird did the same thing when a friend rode it in low gears/ high revs in a hot Florida day with stop and go traffic.

I know parts are expensive for you, but I would get the fan thermostat working again and check the radiator cap. If the cap is not holding the 108-137 kPa, 16-20psi, then you will boil sooner, and more will be discharged to the overflow.

A weak cap, or one with dirt on the seals can cause this problem.

Also, when the bike cooled, did all the fluid in the overflow bottle go back into the radiator? or did the cold level amount remain?

[tomek]

There is no crystal clear answer in alu vs copper debate,at least based on my limited knowleage.

Honestly I think it does not matter in your case of high speed crusing.Whether your fun runs or not is irrelevant here,at 180 it freewheels like crazy anyway.

I would go thru the basics ,radiator cap,hoses routing, especially rad to coolant tank (can coolant flow freely in and OUT ? ),coolant level ( if level is too high bike will keep spewing coolant till it gets low enough) .

[redxxrdr]

I did have an additional thought.

Have you inspected the waterpump?

Cooling requires the correct flows of coolant and air volumes to properly.

I have seen post where the vanes on the waterpump were damaged or gone due to crash or poor coolant. It might be worth a check.

[cbrxxquad]

I tend to think that you have the lines wrong going to the overflow tank. If not then the procedure to get all the air out of the radiator before capping should be looked at. One or the two together could be my impression.

[brianmacza]

I know parts are expensive for you, but I would get the fan thermostat working again and check the radiator cap. If the cap is not holding the 108-137 kPa, 16-20psi, then you will boil sooner, and more will be discharged to the overflow.

A weak cap, or one with dirt on the seals can cause this problem.

The original radiator cap was trashed in the off - the limited research I did indicated that the likely set pressure was 0.9bar - this is probably the culprit if the stock honda cap has a higher standard pressure rating.

Will have to get one and see what the difference is )

[Zero Knievel]

I know it sounds obvious, but could it be the new radiator has a "design flaw" that traps air pockets in when you fill it? We all know those should come out, but the repeated boil over sounds like a common problem if air is still in the system even after you thought you got it all out.

Also, I had a boil-over problem on an old Kawasaki because the hose was wearing out in one place. The problem started with it sucking in air and eventually the hose split, but it was a pain until I replaced both hoses on the system. Even if your hose is good, if it's not seated right and clamped down properly, a flex in the hose might put enough pressure to weaken the seal around the clamp.

[EVLXX]

The upchuck comes from the header bottle - its not steaming hot water, but I'm assuming its propelled by a bubble of steam from the radiator past the 0.9 bar radiator cap pressure spring...

erm... it lands on the floor

Was your overflow bottle full when you started? or filled to the cold fill level?

My bird did the same thing when a friend rode it in low gears/ high revs in a hot Florida day with stop and go traffic.

I know parts are expensive for you, but I would get the fan thermostat working again and check the radiator cap. If the cap is not holding the 108-137 kPa, 16-20psi, then you will boil sooner, and more will be discharged to the overflow.

A weak cap, or one with dirt on the seals can cause this problem.

Also, when the bike cooled, did all the fluid in the overflow bottle go back into the radiator? or did the cold level amount remain?

I did have an additional thought.

Have you inspected the waterpump?

Cooling requires the correct flows of coolant and air volumes to properly.

I have seen post where the vanes on the waterpump were damaged or gone due to crash or poor coolant. It might be worth a check.

+2 on all that...

And it's normal for the coolant to heat up once the bike is turned off.... hence why the radiator fan will sometimes run for a while after you turn off your engine with the kill switch.... "you need to get that fixed, correctly."

and 0.9 Bar does not sound like enough pressure..... If I remember correctly 1 Bar is equal to 7 psi. Which would make 0.9 too low, if your running regular coolant and water mix....

....

[rockmeupto125]

A bar is roughly the air pressure at sea level. I should have caught that. Standard cap for the XX is 16-20 pounds, or 1.1-1.4 bar. Try that, and check your lines as well, as others have suggested.

[EVLXX]

I'll also add...

Maybe this would help you... it runs at zero pressure....

http://www.evanscooling.com/html/npgPls.htm

I see you can get it here...

http://www.aircraftspruce.com/intlreps.html

[redxxrdr]

I haven't shopped Aircraft Spruce in years. They used to be really good to deal with, for just Plane stuff.

Prices on Evans don't look bad. Brochure indicated that it is approved for racing at any place that ethelyne glycol (sp) is used.

Probably not good for Racer XX, but I might try it after, instead of antifreeze.

Thanks for the links.

[brianmacza]

I couldn't get a higher rating rad cap from Honda - they are so fucking useless. Their parts database shows zero stock of radiator caps for ALL models at ALL dealerships, countrywide. SPecial import from Japan will take 21 days and the cost will be ZAR350 (about US$50). Got one from the local Yamaha agent, same spec, in stock, US$8

The new cap makes a world of difference - no overflow after a 50km ride in back streets at low speeds with the fan running intermittently. Will now convert to 100% antifreeze and its business as usual )

Thanks for the help guys...

[BackStreet]

Glad you found the answer; sorry I was too late.

I had a boil over problem recently on a 944 Porsche and it was the radiator cap.

To lower the operating temp and in general improve cooling, get a bottle of RedLine Water Wetter. You only need 1/4 bottle.

BTW - If you need anything from the US; get a paypal account and I'll ship it to you for cost.